Optical films are incorporated in a variety of applications. These films sometimes employ a thin layer of a metal such as silver. Optical films are used in various constructions on flexible substrates to obtain beneficial properties. Representative uses for optical films include solar control films, EMI shielding films, window films, and conductive films. These films often require high visible light transmission, and if metalized, low electrical resistivity.
There is a proportional relationship between optical transmission and resistivity in conductive metal layers. This relationship makes the typical objective, forming a film having both high visible light transmission and low resistivity, a delicate balance because changing the performance of either property can adversely affect the other property. When forming a metal layer, the metal can agglomerate as it is deposited. This can result in a film that is non-homogeneous, and can require application of a relatively thick metal layer to provide a highly conductive film or an effective shielding film. This agglomeration or formation of islands makes the optical transmission diminish and causes an increase in resistivity.
There remains a need for flexible optical films having high optical transmission and high electrical conductivity, and a need for methods for preparing such films.